This is a U.S. original patent application which claims priority on Great Britain patent application No. 0211049.2 filed May 15, 2002.
This invention relates to the field of the protection of photographs from unauthorized copying, i.e. copying that does not have the copyright owner""s consent.
The copying of photographs by parties that do not have the copyright owner""s permission is a problem. Unauthorized copying results in the loss of potential revenue from the possible legal sale of the photographs.
This copyright xe2x80x98theftxe2x80x99 can be prevented in many ways. The photographic print could be marked in a unique way such as by the signing of the print by the copyright owner or the application of a unique visual identification mark. However, these methods may easily be forged by someone skilled in copying as they are readily seen. In addition, a visible marking might detract from the image. The image might be marked covertly, in a way that cannot be seen without the appropriate tool. If the image is digitally produced, the marking can be done by including a code in the digitization that is not visible in the final print when viewed by the eye, but can be detected electronically. Such methods are practiced by Digimarc Inc., disclosed in e.g. U.S. Pat. No. 6,345,104. Another method is to include a series of dots in the image that can only be detected electronically or by a skilled viewer. Such a method is disclosed in EP 0789270.
The invention aims to provide a method which can detect whether a print or film has been processed at an authorized site, i.e. authorized by the copyright owner. Processing at an authorized site uses unique chemistry to process the print. Identification of the presence of the unique chemistry indicates that the prints are printed with copyright consent. Any prints which did not show the presence of the unique chemistry would be shown not to have been processed at an authorized site and unauthorized use would be established.
According to the present invention there is provided a method of processing a photosensitive material in which at least one of the processing solutions includes one or more chemical compounds which are at least partially retained in the material after processing is complete, the structure and composition of the compounds being unique to a particular process used by a particular copyright owner.
Preferably, but not necessarily, the chemical compounds are added to the stabilizer or wash solution.
The present invention allows a print to be linked with a particular processing establishment or even a particular processing machine.
It is possible for the method of the invention to be used for motion picture prints as well as conventional prints.
The invention is almost impossible to xe2x80x9creverse engineerxe2x80x9d. Analysis of the processed material will not give the proportion of chemicals added, i.e. the proportion left is not directly derivable from what goes in.